MONDAY, July 6, 2015 (HealthDay News) -- Many health care professionals work when they are sick, putting their patients at risk for serious illness or even death, new research suggests.

The danger is greatest for patients with weakened immune systems, and the study authors noted that these practices also increase health care costs.

Since the consequences of these types of infections can be significant, the researchers wanted to know why health care professionals didn't stay home when they were ill.

So, they surveyed doctors, nurse practitioners, physician assistants, nurse anesthetists and midwives. A team of researchers, led by Julia Szymczak of the Children's Hospital of Philadelphia, received anonymous responses from more than 500 health care professionals.

The vast majority of those surveyed (95 percent) believed that working while sick put their patients at risk. Still, 83 percent admitted to working while sick at least once in the past year and 9 percent said they worked while sick at least five times. They said they worked with symptoms like diarrhea, fever and significant respiratory issues, the study published online July 6 in the journal JAMA Pediatrics showed.

And why do they work when sick?

Almost 99 percent didn't want to let their colleagues down,

Almost 95 percent had concerns about staffing,

92.5 percent didn't want to disappoint their patients,

64 percent were worried about being ostracized by their colleagues,

Almost 64 percent were concerned about continuity of care.

"The study illustrates the complex social and logistic factors that cause this behavior," the researchers said in a journal news release.

Lowering the stigma that can come with sick leave "must factor in workplace demands and variability in patient census [count] and emphasize flexibility," Dr. Jeffrey Starke, of Baylor College of Medicine in Houston, and Dr. Mary Anne Jackson, from the University of Missouri-Kansas City School of Medicine, wrote in a related editorial. "Also essential is clarity from occupational health and infection control departments to identify what constitutes being too sick to work."